The present invention relates to a vertical internal combustion engine, and particularly relates to a four-stroke water-cooled vertical internal combustion engine suitable for use in an outboard marine drive.
In four-stroke water-cooled vertical internal combustion engines for outboard marine drives, it is necessary to mount various component parts on top of the engine. Such component parts may include a tension pulley that is spring-biased to contact a timing belt, a fixed pulley for guiding or defining the path of the timing belt, component parts for achieving cooling of the engine, such as a thermostat valve, etc. Thus, it is required to provide a sufficient space for mounting these component parts on top of the engine as well as simplify the mounting process thereof.
It is also desired to use manufacturing lines for the mass-produced automobile horizontal engines commonly in manufacturing the vertical engines which are usually produced in a relatively small number, so that the basic design, component parts and/or manufacturing equipment such as machine tools may be used in common, which can bring about significant economical benefits. In such a case, however, some of the parts mounted on the horizontal engine, such as a water pump, may have to be mounted to a different part of the vertical engine. This may leave a large opening in the top surface of the vertical engine which extends to the water jacket, and limit the freedom of parts arrangement on top of the engine to such an extent that the proper arrangement of the component parts becomes difficult.
Conventional embodiments of such engines are disclosed in Japanese Patent Registration No. 2524102 or Japanese Utility Model Application Laid-Open Publication (kokai) No. 63-128, for example.
In view of such problems of the prior art, a primary object of the present invention is to provide an improved water-cooled vertical internal combustion engine in which a sufficient space can be provided for the component parts mounted on top of the engine and the mounting process of such component parts can be simplified.
A second object of the present invention is to provide an improved water-cooled vertical internal combustion engine wherein the parts arrangement on top of the engine can be relatively freely designed even when the vertical engine is manufactured by commonly using a manufacturing line for a horizontal engine.
According to the present invention, such objects can be accomplished by providing a vertical internal combustion engine, comprising; a cylinder block; a cylinder head connected to an end of the cylinder block; a crankshaft extending generally vertically and rotatably supported in the cylinder block; a camshaft extending generally in parallel with the crankshaft and rotatably supported in the cylinder head; and a timing belt for connecting pulleys provided to upper end portions of the crankshaft and the camshaft so as to transmit a driving force from the crankshaft to the camshaft, wherein the engine further comprises a plate attached to a top surface of the cylinder block and at least one idle pulley rotatably supported by the plate and contacting the timing belt.
In this way, it is possible to attach the at least one idle pulley to the plate to form a sub-assembly, and then attach the sub-assembly to the top of the engine, which can significantly simplify and facilitate the mounting of the pulley(s) to the top of the engine.
When the cylinder block has a water jacket for cooling the engine, it is preferable that the plate sealably closes an opening formed in the top surface of the cylinder block and extending to the water jacket. Such an opening may be formed when a manufacturing line for a horizontal engine is commonly used in manufacturing the vertical engine due to a different mounting position of a water pump, for example. Thus, by sealably covering the opening by the plate for supporting the idle pulley(s), it is facilitated to manufacture the vertical engine by commonly using the horizontal engine. The opening of the cylinder block may accommodate a component part, such as a thermostat valve, of a water cooling system so that the opening is effectively used.
The at least one idle pulley may comprise a spring-biased tension pulley and/or a fixed belt guiding pulley. Preferably, the at least one idle pulley comprises more than one idle pulley. In this way, it is possible to mount the more than one pulley to the cylinder block by attaching the common supporting plate to the cylinder block. This can reduce the number of required bolts for attachment and thus reduce the space required for them, which can leave a larger space for idle pulley arrangement to thereby facilitate the arrangement of such component parts.
The engine typically consists of a four-stroke V-type internal combustion engine suitable for an outboard marine drive.
Other and further objects, features and advantages of the invention will appear more fully from the following description.